One drawback in the previous setup is that we had to use one transistor per digital output (to control a device powered by another source).
\nThat is 8 extra transistors, 8*3 extra wires, etc : not very practical and especially if we intend to control several shift registers IC’s. (i plan on using 3 in my wordclock project)<\/p>\n
So this is where the ULN2803 <\/a>comes in : 8 NPN transistors and one common ground in one integrated circuit.<\/p>\n See below a refreshed schema (compared to the previous article). Note that I have decided to power my IC’s with my (regulated) Arduino 5v but I could as well have used my battery pack power. the Arduino sketch :<\/p>\n Still on my journey to a wordclock… In the previous article, we have seen how to use a shift register to control up to 8 digital outputs (or more if you cascade IC’s). One drawback in the previous setup is that we had to use one transistor per digital output (to control a device powered […]<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18],"tags":[51,50],"class_list":["post-1288","post","type-post","status-publish","format-standard","hentry","category-arduino","tag-74hc595","tag-uln2803","category-18-id","post-seq-1","post-parity-odd","meta-position-corners","fix"],"_links":{"self":[{"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=\/wp\/v2\/posts\/1288","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1288"}],"version-history":[{"count":13,"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=\/wp\/v2\/posts\/1288\/revisions"}],"predecessor-version":[{"id":1309,"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=\/wp\/v2\/posts\/1288\/revisions\/1309"}],"wp:attachment":[{"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1288"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1288"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/labalec.fr\/erwan\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1288"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"uln2803\"](\"https:\/\/labalec.fr\/erwan\/wp-content\/uploads\/2014\/06\/uln2803-207x300.jpg\")
<\/a><\/p>\n
\nOur 74HC595 will control our ULN2803 (by sending HIGH or LOW on the input) which in turn will drive the current thru each output\/led.<\/p>\n![\"uln2803a_bb\"](\"https:\/\/labalec.fr\/erwan\/wp-content\/uploads\/2014\/06\/uln2803a_bb-1024x629.png\")
<\/a><\/p>\n\/\/the pins we are using\r\nint latchPin = 2;\r\nint clockPin = 3;\r\nint dataPin = 4;\r\n \r\nvoid setup() {\r\n \/\/set all the pins used to talk to the chip\r\n \/\/as output pins so we can write to them\r\n pinMode(latchPin, OUTPUT);\r\n pinMode(clockPin, OUTPUT);\r\n pinMode(dataPin, OUTPUT);\r\n}\r\n \r\nvoid loop() {\r\n for (int i = 0; i < 8; i++) {\r\n \r\n \/\/take the latchPin low so the LEDs don't change while we are writing data\r\n digitalWrite(latchPin, LOW);\r\n \r\n \/\/shift out the bits\r\n shiftOut(dataPin, clockPin, MSBFIRST, i); \r\n \r\n \/\/take the latch pin high so the pins reflect\r\n \/\/the data we have sent\r\n digitalWrite(latchPin, HIGH);\r\n\r\n \/\/ pause before next value:\r\n delay(1000);\r\n }\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"